Galactic longitude dependent galactic model parameters

Abstract We present the Galactic model parameters for thin disc estimated by Sloan Digital Sky Survey ( SDSS ) data of 14 940 stars with apparent magnitudes 16  g 0  ⩽ 21 in six intermediate latitude fields in the first Galactic quadrant. Star/galaxy separation was performed by using the SDSS photometric pipeline and the isodensity contours in the ( g  −  r ) 0  − ( r  −  i ) 0 two colour diagram. The separation of thin disc stars is carried out by the bimodal distribution of stars in the ( g  −  r ) 0 histogram, and the absolute magnitudes were evaluated by a procedure presented in the literature (Bilir, S., Karaali, S., Tuncel, S. 2005. AN 326, 321). Exponential density law fits better to the derived density functions for the absolute magnitude intervals 8  M ( g ) ⩽ 9 and 11  M ( g ) ⩽ 12, whereas sech/sech 2 laws are more appropriate for absolute magnitude intervals 9  M ( g ) ⩽ 10 and 10  M ( g ) ⩽ 11. We showed that the scaleheight and scalelength are Galactic longitude dependent. The average values and ranges of the scaleheight and the scalelength are 〈 H 〉 = 220 pc (196 ⩽  H  ⩽ 234 pc) and 〈 H 〉 = 1900 pc (1561 ⩽  h  ⩽ 2280 pc) respectively. This result would be useful to explain different numerical values claimed for those parameters obtained by different authors for the fields in different directions of the Galaxy.